Computer networks have grown increasingly complex with the use of distributed client/server applications, mixed platforms and multiple protocols all on a single physical backbone. The control of traffic on the networks is likewise moving from centralized information systems departments to distributed workgroups. The growing utilization of computer networks is not only causing a move to new, high-speed technologies but is at the same time making the operation of computer networks more critical to day-to-day business operations.
The growth in complexity and dependence on computer networks heightens the need for network management tools to design, build and maintain computer networks. The mix of protocols and vendors of installed hardware on many computer networks generally increases the difficulty of accomplishing network management. This problem may arise in planning or designing changes to a network, monitoring performance of a network, and testing the impact on performance of different hardware and software being installed on a network. A variety of approaches to network management tools have been considered including, frame generators, passive monitors, simulation tools, and applications testers. However, each of these categories of network management tools may have its own limitations affecting a users ability to manage increasingly complex and critical computer networks.
Frame generators are typically used for performance and stress testing of network equipment. Typically, they are network analyzers with the ability to send as well as receive data. An example of a frame generator is the DA-30 from Wandel & Goltermann. Another example is SmartBits by Netcom Systems. SmartBits generates packets with fixed- or variable-length gap and packet contents while receiving packets. SmartBits provides for multiple modular ports mounted in a chassis for testing and monitoring internetworking equipment. On the receive side, each card contains counters to monitor the number of packets transmitted, received, collisions, byte count, triggers and certain errors or to monitor the rate of each parameter. A Windows programming interface allows the individual cards to be programmed. Various industry standard bench tests are supported. A third example is LANQuest Net/WRx which enables creation of traffic streams between a sending and receiving node for routers, bridges, hubs, switches and servers acting as routers. Net/WRx provides testing for new and existing network products for interoperability and functional operation. Net/WRx is designed to test product designs for network products. Frame generators are typically specialized, single-purpose hardware which may be connected to a network to be tested during a test. This can result in high costs, particularly if it is desirable to test a plurality of points requiring multiple systems to be connected for the test. Frame generators are also generally limited in their ability to test network performance under actual application conditions as they typically do not operate on communication nodes of the network to be tested but are instead hardware testers installed to test the network. In addition, they typically operate at layer 2 of the networking model, the link layer. Therefore, typically no real protocol stacks running on the network are used for testing again removing the test from the actual conditions under which the network to be tested would be used.
An alternative type of network management tool is a passive monitor. Passive monitors are a combination of hardware and software that typically monitor network traffic at the link layer. They are passive in that they watch the network traffic that is flowing rather than actively creating traffic. Passive monitors may be categorized as network analyzers, like Network General's Sniffer, and remote monitors, such as NETscout from Frontier Software Development, Inc., EcoNET from Compuware Corporation, and Vital Signs from VisionNet. However, these tools may also include various limitations. Because they monitor at the link layer, to get a complete picture of performance a monitor is typically required at every network segment, generally causing increased expense and setup requirements. These devices also are limited in that they may only monitor existing traffic as its passes them and may not test by generating predetermined traffic flow patterns.
Another network management tool is a simulation tool. Simulation tools provide a mathematical model of a network. The model is generated based on information about network design, hardware, and traffic patterns. Once the model is created, it can be used to predict network performance under different scenarios. However, these tools are generally limited in their ability to accurately model the network and update the model as the network is changed. In addition, various network problems can arise from subtle differences in configuration, queuing, congestion control and frame sizes which are typically difficult to model. Furthermore, they typically only simulate network performance for when a network is working correctly rather than identifying problems.
A fourth category of network management tools is application testers. These types of systems vary greatly but generally act by driving installed applications on a network. The testers typically simulate a user reading screens and typing at a keyboard to create network traffic. Such programs are generally intended to aid application developers, not network managers. Typically, the application must be available and installed before these tools can be utilized by a network manager. An example of such a test tool is QA Partner from Seque Software, Inc.
Various other testers aimed at addressing particular aspects of network management are available. ProView-SNA utilizes active traffic generation to measure network performance characteristics by monitoring round trip response times to SNA hosts and to LAN file servers. Under control of a ProView Management Station, Remote Agents execute application layer transactions, compute round trip response time and forward the results to the Management Station for display and storage. NetBench is a Ziff-Davis benchmark program that measures the performance of servers in a file server environment. It provides a way to measure, analyze, and predict how a server handles network file I/O requests from client computers in a file server environment.
These network management tools are generally limited in their ability to support multiple protocols and to test networks under actual operating conditions. It is increasingly important to analyze the actual performance of the network to be tested without the constraints and limitations of these existing tools. Additionally, scalabilty of tests, distributed testing and a means to test all types of network devices would provide greater testing flexibility to network managers.